Re: [tip:core/signals] signals/sigaltstack: Prepare to add new SS_xxx flags

[Andy Lutomirski]

On Tue, May 3, 2016 at 9:13 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> On Tue, May 3, 2016 at 12:50 AM, tip-bot for Stas Sergeev
> <tipbot@xxxxxxxxx> wrote:
>> Commit-ID:  407bc16ad1769f5cb8ad9555611cb198187ef4cd
>> Gitweb:     http://git.kernel.org/tip/407bc16ad1769f5cb8ad9555611cb198187ef4cd
>> Author:     Stas Sergeev <stsp@xxxxxxx>
>> AuthorDate: Thu, 14 Apr 2016 23:20:03 +0300
>> Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
>> CommitDate: Tue, 3 May 2016 08:37:59 +0200
>>
>> signals/sigaltstack: Prepare to add new SS_xxx flags
>>
>> This patch adds SS_FLAG_BITS - the mask that splits sigaltstack
>> mode values and bit-flags. Since there is no bit-flags yet, the
>> mask is defined to 0. The flags are added by subsequent patches.
>> With every new flag, the mask should have the appropriate bit cleared.
>>
>> This makes sure if some flag is tried on a kernel that doesn't
>> support it, the -EINVAL error will be returned, because such a
>> flag will be treated as an invalid mode rather than the bit-flag.
>>
>> That way the existence of the particular features can be probed
>> at run-time.
>>
>> This change was suggested by Andy Lutomirski:
>>
>>   https://lkml.org/lkml/2016/3/6/158
>
> LGTM.

Correction: does not LGTM.  In a sensible design, sigaltstack would
report flags back to the caller.  I will send a fix.

--Andy